Endoscopic technology allows devices to be introduced into the human or animal body and manipulated external to the body. The terms endoscope and endoscopic are used herein to broadly encompass medical or veterinary devices or instruments such as laparoscopes, cytoscopes, colonoscopes, sigmoidoscopes, arthroscopes, esophagoscopes, bronchoscopes, gastroscopes, thoracoscopes, peritoneoscopes, culdoscopes, catheters and the like which are designed to penetrate a body structure, cavity, orifice or lumen and to permit some sort of procedure or therapeutic action. The term "probe" as used herein is intended to include any endoscopic device.
Many of the body cavities and hollow conduits (e.g. peritoneal, abdominal, bronchial, lung, esophagal) can be accessed through endoscopic means without surgical incisions and trauma associated with such incision. Endoscopes typically include a long, thin tubular casing or shaft optically connected to viewing mechanism. The probe shaft is narrow enough to insert through small openings, either natural or surgical, in the body and thereby enter a bodily cavity. As used herein, bodily cavity is intended to include any and all mammalian body cavities, including but not limited to colon, duodenum, esophagus, trachea, bronchii, stomach, lungs, arteries, veins, capillaries, vagina, uterus, gall bladder, ureters, kidneys, peritoneal, and thoracic cavities, synovial spaces, spinal cord cavity, urethra, ducts, and organs such as eye, heart and the like.
Endoscopic technology led to a technique for ultrasonically scanning the heart: transesophageal echocardiography, or TEE. In TEE, an ultrasonic transducer is located at the end of an elongated probe, which is passed through the patient's mouth and into the esophagus or stomach. From such a position within the thoracic cavity, the ribs no longer impede the transmission or reception of ultrasound.
However, in many procedures, the minimization of trauma or discomfort to the patient is paramount. The probe shaft must be smooth on the external surface, facilitating comfortable insertion. The probe shaft must also be flexible, thereby conforming to contours inside the patient's body. Moreover, in a climate of upward spiraling medical related costs, manufacturing, maintenance and repair cost containment is sought for ubiquitous devices such as probes and probe shafts.
Currently used scopes are constructed with a crush proof inner core within which the electrical and mechanical components reside, a sheath element associated with the core to provide torsional stiffness in order that the probe may be rotationally controlled, and some sort of scaled protective coating.
Proper coating of any probe shaft is vital to minimizing trauma and facilitating entrance of the probe into the desired structure or cavity, as well as to protect the probe from body fluids and other fluids capable of damaging the probe elements. The protective coating of the shaft also serves to insulate the patient from contact with electrical components.
The trade off with elastomeric coatings is between flexibility and strength. The more flexible the coating, the more susceptible is the coating to being pierced by a patient's tooth or otherwise abraded or lacerated. Laceration of the protective coating renders a probe shaft virtually unusable, as it can no longer protect the patient from electrical contact with the core, nor can the probe shaft be adequately sterilized.
Current manufacturing methods for covering endoscopic tubing include multiple steps and are limited by the curing time of the primer and polymer coating selected. A commonly practiced method includes selecting a main metallic shaft or core (generally, a steel monocoil--a helically wound metallic strip--covered by a steel braid) and covering the metallic shaft with an extruded thermoplastic tubing suspended in an expanded state in a vacuum. After the metallic shaft has been inserted into the vacuum-expanded extruded tube, the vacuum is removed, and the extruded thermoplastic tubing conforms tightly around shaft. This method, however, requires a primer be applied to the external surface of the steel braid to ensure adhering of the thermoplastic tubing to the metallic shaft.
Another method currently practiced includes priming the surface of the steel braid, followed by application of a thermosetting polymer and curing (cross linking) of the polymer. In this method, thickness uniformity is not easily controlled, and the primer and curing steps both consume valuable manufacturing time.
Further adding to the cost of probe maintenance is the wearing off of depth markings. Depth markings are painted on the exterior of the protective coating and indicate the depth to which the probe has been inserted. The wearing off of depth markings requires the probe be returned for repainting, adding to the need for additional instrument inventory as well as increasing the maintenance cost of the equipment.